1. Field of the Invention
This invention relates to metalworking and more particularly to a mechanical process by flaring an inserted tube end or expanding a part in an aperture or radial expanding an internal fitted tube.
2. Description of the Prior Art
The prior art of metalworking has known many types of tube and fitting assemblies wherein a tube and fitting are joined without the aid of threads, nuts, and the like. Generally, the tube or fitting is deformed or swaged to seal the tube to the fitting.
In many cases, the swaging or deformation process causes a cold welding of the tube and fitting due to the extremely high pressures exerted between the tube and fitting. Cold welding was generally accomplished on softer materials such as aluminum and the like. One disadvantage of cold welding is that the weld only takes place when the materials were freshly cut or prepared. If aluminum parts were stored for any substantial period of time then no cold weld would form due to aluminum oxide on the surface.
The prior art has joined tube and fitting assemblies by inserting a tube into a fitting and using a flaring tool to expand the tubing wall to engage the fitting. For example, a fitting bore may have a recess wherein the tubing wall is radially expanded by a flaring tool to engage the bore recess to form a seal between the tube and the fitting. This process was suitable for larger tubings but was impractical for small tubings where a flaring tool cannot be easily inserted.
The prior art has used a ring stake process to join a small tube to a fitting. The ring stake process incorporates a fitting having a single bore substantially the same diameter as the tube. The tube is inserted into the bore and a die swages an outside surface of the fitting surrounding the bore to cause a deformation of the fitting to engage the tubing wall. This process did not require any internal flaring tool and provided a satisfactory low-pressure seal so long as no torsional strain was applied between the tube and the fitting. However, the seal could be destroyed if a torque was applied between the tube and the fitting about the axis of the tube. Consequently, the ring stake tube fitting assembly proved unreliable for many applications.
Therefore, an object of this invention is to provide a method of making a tube fitting assembly which requires no cold welding.
Another object of this invention is to provide a method of making a tube fitting assembly which requires no internal flaring tools.
Another object of this invention is to provide a method of making a tube fitting assembly which can be formed in a one-step operation.
Another object of this invention is to provide a method of making a tube fitting assembly which has a high torsional strength.
Another object of this invention is to provide a method of making a tube fitting assembly which is capable of high pressure sealing.
Another object of this invention is to provide a method of making a tube fitting assembly which is reliable.